1. Field of the Invention
The invention relates to a roller bearing that is lubricated with a lubricant containing foreign matter.
2. Description of the Related Art
A tapered roller bearing is known which is assembled in a transmission, a differential, or the like in automobiles, various construction machines, and the like and which is lubricated using a lubricant (oil) that lubricates a power transmission mechanism such as a transmission or a differential. The lubricant is housed in a case of the power transmission mechanism and contains a relatively large amount of foreign matter such as wear debris (iron debris) from gears.
Thus, the foreign matter contained in the lubricant enters into the roller bearing. Consequently, the foreign matter is trapped on raceway surfaces of an inner ring and an outer ring and rolling surfaces of tapered rollers to peel off the raceway surfaces and the rolling surfaces. This may make the tapered roller bearing less durable. Therefore, a conventional tapered roller bearing has been proposed in which an axially outer opening in an annular space between an outer ring and an inner ring is covered by a seal apparatus so as to prevent foreign matter from entering into a bearing interior (see, for example, Japanese Patent Application Publication No. 2014-231856 (JP 2014-231856 A)).
However, this tapered roller bearing needs the seal apparatus that suppresses entry of foreign matter. This disadvantageously increases the number of components of the tapered roller bearing and complicates the structure thereof.